Fogageddon

I suppose if I truly want to take the weekend off, I’ll have to ditch my smartphone. These photos from the Facebook page of the Panhandle Helicopter Service in Panama City Beach, Florida, have been making the rounds today, erroneously labeled by ABC, MSNBC, and other news outlets as a “tsunami cloud”. Hence my humorous headline. Here’s the pictures in a clickable gallery:

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The explanation for this phenomenon is very simple.

Nearly saturated (at almost the dew point) air from a sea breeze is being lifted (Orographic lifting) as it meets the coast and the buildings. The slight cooling from the lifting cools the air to the dew point and clouds form.

A similar phenomenon can be seen on some ocean islands.

Luytla-Duymun Island, part of the Faroe Islands - Image shot by Spumador and is located on Flickr

But does it really hold for an island-like feature when it may be “easier” for the air to move around the obstruction, than over it? (After Le Chatelier’s principle)

(Sticking my head out, displaying how little I know.)

Obvious variables to consider are density (variable with water vapour content), free velocity, height of obstacle and the “width” of the obstacle. Surface “roughness” comes into play because that affects the vertical velocity (and pressure) distribution of the air.

In the mountains we have “lenticular clouds” that scramble people’s thinking processes if they haven’t seen them before and don’t understand lapse rates. Some people think they’re UFOs. The Plymouth State University Cloud Boutique has several (for free).

In the Luytla-Duymun Island picture is similar to what I saw off one of the headlands (Where “The Metal Man” is) around Tramore, Waterford, Ireland back in the late 70’s. Fog was slowly drifting over one of the headlands and then eventually settling on the sea. Awesome to watch, but that’s about it.

Temperature and humidity very close to the dew point. Last September I flew from London to Mallorca (Spain). The weather was clear but cool and visibility was very good on land. When we got to the English channel, the sea was covered with a thin but dense layer of fog which stopped at the shoreline. If there had been an onshore wind, there would have been similar foggy effects as in the pictures. As they say, it’s weather.

Although no nuclear power plants were damaged by the “fog tsunami”, GreenPeace immediately issued a press release calling for their shutdown until they could be reinforced against fog damage and proven to be safe.

“…But does it really hold for an island-like feature when it may be “easier” for the air to move around the obstruction, than over it? (After Le Chatelier’s principle)

(Sticking my head out, displaying how little I know.)…”

In technical terms I know even less, though I often ‘slope-soar’ my models on such a wind. In my experience air finds it slightly easier to go over an obstacle than to go round it – I always thought that was because the air above an obstacle is higher, so at a slightly lower pressure than the air at the sides. Thus it’s ‘easier to push out of the way’….

Not only does the slight temperature change bring the air to dew point, but the air speed has an important role too. The entire air front facing these buildings has to go through limited openings (above buildings). As a result, the air flow speed increase.
Pressure decrease when speed increase. And with pressure decreasing you reach the dew point.

Same thing happens on top of airplane wings (in this case there is no elevation change, only effect of air acceleration bringing down pressure):

I have often used this phenomena when navigating around the pacific islands in the days before everyone had access to sat nav gear. If you have an isolated island you start to look for a stationary cloud. All the clouds will be drifting down wind, except the one that sits on the high point of the island.

They often have something of an anvil shape at the top of the cloud drifts down wind a little, before dissipating.

If the island has a coral lagoon you can also see the reflection of the turquoise water in the cloud, where the others will be white.

I grew up in Panama City, my father was stationed at Tyndall AFB. We would have never seen this as there was nothing tall enough on the beach to cause any updrafts. When I went back to the panhandle a couple of years ago I found out that you could walk from PC to Ft. Walton without ever stepping off of some hi rise condos property, gone was the open beach of the past. No wonder hurricane damage is up, it has nothing to do with the strength of the storms.

Anthony, I thought you disliked illiteracy? I’m not trying to pick on you, just trying to point out common grammatical mistakes so your blog is a better read. Please take this as constructive criticism, not as an attack.

A very good picture of Windfarms affecting climate they are lifting the air from the surface and also possibly causing Venturi cooling around their blades resulting in bands of stratocumulus which spread and form a layer of stratocu behind the windfarm. This will cool the surface in the daytime and reduce the cooling at night. I wonder if there are similar pictures of windfarm caused clouds for on-shore sites? This could cause issues with crops downwind of the windfarms.

Tsunami clouds
Bring the warmist shrouds:
When the weather’s strange
Heralds Climate Change,
Your time is coming to an end.

Give it up, Al, Jim and Joe
Your tsunami clouds
Bring a furrow to our brows.
Each day, somewhere
You see a cloud to give us a scare
Give it up, Al, Jim and Joe:
We’re seen through your tsunami clouds
We all know that you’re only in it for the dough,

Ian W says:
February 12, 2012 at 9:53 am
“daytime and reduce the cooling at night. I wonder if there are similar pictures of windfarm caused clouds for on-shore sites? This could cause issues with crops downwind of the windfarms.”

It is known that they cause more turbulence near the ground in their wake, leading to higher evaporation.

Fritz Vahrenholt and Sebastian Luning have a new website for visitors who are conversant in German language.
———————————————————-
Die Kalte Sonne
Warum die Klimakatastrophe nicht stattfindethttp://www.kaltesonne.de/

PKatt sez: “Go to SF in the summer sometime its basically the same thing.” –My fist thought, exactly. The fog rolling over the first line of hills along that stretch of shore. This phenomenon is not suprising to locals of Bay area.

Silver RalphNever mind the small cap-clouds on the hotel blocks — the most exciting thing is the upper clouds just inland. With a decent glider, you could soar that sea-breeze front for hundreds of kilometers…
Have done SR, many times, though the fronts are frequently not so obvious, they are there just about any day there’s an offshore wind in land.

Anthony

Ever slope soared a cumulus? On occasion a marked wind shear (direction & speed) occurs at cloudbase, with cumulus depths > 500ft it is possible to slope soar the into wind face of the cumulus and climb well above cloudbase just as one slope soars a mountain ridge facing the wind, on occasion flying around/through orographic cloud forming just upwind of the mass of the cumulus capped thermal exactly as the cloud is forming upwind of the tower blocks in the images.

Even less occasionally, one can see a shadow of the glider on the cumulus surrounded by a circular rainbow as the orographic droplets refract sunlight as a zillion prisms, yes, it’s a privilege to see it

And finally, depending on the depth of the cumulus and the wind shear angle/speed increase with height, it’s even possible to transition into a lee wave system, oriented on the sea breeze (or even well marked cloud streets) generated by the slope lift off the cloud (again similar to lee wave systems from mountains) permitting a climb to ‘000’s of ft above the source and yet more extraordinary vistas

Back in the early ’90’s my wife (career Navy) had the good fortune to be stationed at a tiny little Communications Station in Thurso, Scotland. Just about as far north as you can get. Our kitchen window looked out over Thurso Bay across Scapa Flow to Hoy (southern most of the Orkney Islands). On a clear day we could see “The Old Many of Hoy”. More often then not, we’d see fog phenomena just like this over the Orkney’s. Beautiful place to live with some truly lovely people (before they ravaged the landscape with windmills).

Jeff Alberts says:
February 12, 2012 at 8:02 am
========
The last two posts on your website r dated 1/15/2012 and 12/12/2011, and discuss Tim Tebow.
The grand total of comments on said posts is zero.
The grand total of comments on your last 4 posts is zero.
No wonder you have nothing better to do than try to hassle Anthony.
Get a life.

Don’t forget Bernoulli’s principle. The air in going around up, over, under an obstruction must speed up to maintain the flow, and so the pressure must drop in going through the venturi, so the air density lowers, and the dew point rises (in Temperature) so condensation occurs.

I see it quite often around automobiles driving along a roadway after a rainstorm in high humidity conditions. You think it is just water spray being kicked up by the tires off the wet road, yet you see it when there is virtually no water left on the road, and the fog forms ahead of the tires anyway.

Possibly related but very interesting for discussion. Hope someone can discuss this intelligently digging into the physics. Led me into atmospheric research years ago. I was suprised at how many ‘experts’ and engineers only give the cause a light dusting over.

Visualize a sonic boom. The following URL has got to be the longest I have ever copied. Try searching “F 14 sonic boom” then click on “images for f 14 sonic boom”. The 6 th image of F 14 appears to be flying through a frisbee. Amazing photos but will make you think hard if you want to fully understand why it happens.

this phenomenon is caused by changes in pressure, not temperature. and, as counterintuitive as it sound, the areas with the fog have a HIGHER static pressure than the other areas. the buildings cause a stagnation of the flow of the high humidity air flow oof of the water, raising the static pressure and creating the condensation

as eyesonu points out, a similar effect is seen on near super-sonic jets in high humidity as the expansion shock wave raises the static pressure (note that in this case the stagnation pressure actually goes down but thats another story)

this effect is caused by the expansion shock wave that occurs (roughly) at the point of maximum cross-sectional area of the plane. at that point the static pressure of the air goes up (from one side of the shock to the other), which results in the condensation of the vapor water in the air. there is also a compression shock wave at the nose of the plane but at that point the staic pressure actually goes down so no liquid water.

I want to understand every aspect of this phenomenon with regards to the ‘frisbee’ effect.

My theory was that a shock wave was continiously generated that was radiating outwards and the leading edge was traveling forward with the aircraft at the speed of sound ( say SOS) prior to the aircraft exceeding the SOS. Once the SOS was exceeded there would be a similar shock wave radiating outward but it would be generated ahead of the prior sub SOS wave and would collide thus creating the frisbee cloud. I was not certain if that collision resulting in condensation would have resulted in a point of higher pressure of the waves colliding or at a point of lower pressure just behind the point of the collision of the two waves. If this is correct, is the cloud actually formed in the high pressure point or immediately behind it at a lower pressure point?

A couple of questions:

1) At what speed does the shock wave travel creating the condensation (speed of sound ?).

2) If I read you correctly, then the condensation effect is caused directly as a result of high pressure.

3) Where could I find a very detailed explanation of this.

Inquiring minds need to know. I can then add it to my vast wealth of useless knowledge.

i studied this type of thing for several years in grad school and still dont understand “every aspect” of it but I will give it a shot

first off, envision the plane without wings, so it is basically a cone- at the front edge (point) of the cone, a bow wave is formed, that, if you are going fast enough, becomes a shock wave. based on ideal gas theory (which is a usually good approximation in air), the actual value for this is the square root of–( gamma(ratio of specific heats)xR(ideal gas constant)xT (absolute temperature) )
if you get all the units right this comes out to about 350 m/s or 775mph at 25C.
on the front side of this shock wave the air is still, on the back side there has been a step change in fluid properties- the total pressure (static plus velocity component) has INCREASED, hence the term compression shock. however, the static pressure (the measured pressure) has gone down. now the air follows the cone politely until it encounters another change in direction, in this case where the fusilage of the plane begins to taper off- at that point there is another shock wave formed called an expansion shock- in this case the total pressure goes down, but the static pressure goes up. it is this change from a lower to a higher (a gradient) pressure that creates the condensation. it looks cool in this case because it occurs over a shock wave so it is basically a line in the sky.

incidentally, these two shock waves are what you hear (or used to hear) in when the space shuttle would land. two booms, the leading edge compression wave and the trailing edge expansion wave. you dont typically hear this on smaller planes that are closer to you because the two waves are right on top of each other

finally- the “bible” of compressible flow is considered to be two books by a guy named Ascher Shapiro in the 50’s

a couple other interesting things- if you look carefully at one of the photos on the link you provided you can see the same effect on the back side of the pilots canopy- that is also an expansion wave that is creating the liquid water

if you are REALLY interested, look up how the SR-71 uses the compression wave formed at the cone coming out of the front of the engine to generate more power

That ‘cloud’ formed behind the canopy was what led me to believe that the cloud was formed due to a drop (low) in pressure which would would cause a drop in temp. From that cloud formed behind the cockpit led me to try to understand the ‘frisbee’ effect.

A different ‘cloud’ effect that I attributed to a sudden drop in pressure causing a drop on temp was that seen above the wings when a high speed aircraft makes a sudden ‘upturn’ with relation to the pilots positioning / viewpoint. This was much easier to understand without tossing in the breaking of the SOS.

I still haven’t found the answer to what may be an elementary question: If a gas (air) w/ moisture is suddenly compressed, will it create a cloud or condense the moisture; or would that happen with the sudden expansion?

I wondered about the use of the term “orographic” to refer to this sea-level phenomenon, since (I thought) the root “oro” means “mountain”. I looked it up and found that oro is also linked to the word “rise”, so… guess that’s how it applies. Orogenesis is “mountain-making, especially by folding of the earth’s crust.”

I wondered also if this wasn’t the term for the cloud-making process on Kilimanjaro. Googling “orographic uplift kilimanjaro”, ALL the top seven featured articles (the first page on my screen) appear to acknowledge this “land use” phenomenon on Kili, using variations like “orographic clouds”, “orographic uplift”, “orographic lift”, “orographic precipitation”. Even a NOVA “interactive” (make your own cloud) cites this science without reference to AGW.

A small triumph.

One of those articles, btw, explains the process in terms very familiar to readers here ; – )

to answer your “elementary” question, if it is done suddenly, which would be appropriate for a shock wave or in the wind over the hotel or the shedding vortices on a plane wing (basically most types of fluid flow situations) the event will occur ISOTHERMALLY (temperature will remain roughly constant) and the increase in pressure will result in condensation to occur. however, if it is done gradually over time, as is the case with weather patterns, the process is largely ISENTROPIC (no change in entropy) and the increase in pressure will also result in an increase in temperature so the relative humidity will actually go down.

however, as I said- at a constant temperature, an increase in pressure will increase the relative humidity and COULD result in condensation if the change is sufficiently large

one other thing- fog and rolling mists and marine layers are a different phenomenon than what is seen on the hotels. they are indeed temperature driven scenarios that occur from the cooling of large masses of high humidity air. the dead giveaway are the flowlines that are evident on the hotels or the other examples- that indicates it is a flow induced (and therefore pressure induced) phenom

I started todays ‘trek’ by accessing the publication by Ascher Shapiro, Fundamentals of Compressible Flow Mechanics, (it is available online) and that led me to a publication by Leroy Henderson, General Laws for Propagation of Shockwaves Through Matter, (also available online). That leads to yet deeper analysis as I have yet to find the inclination to dive into. I’ve got to quit asking myself questions!

The SR-71 reading detailing the compression wave formed at the cone of the engine intake was also very interesting.

Thanks again for the exchange, or in my case the gain, of knowledge. Once again, it’s that vast wealth of useless knowledge thing. ;-)

@ JPS or anyone who may have gotten curious with regards to the OT discussion of a condensation cloud formed at the point of the creation of a sonic boom

It seems that I was searching for an answer and it may have been “the tipping point” all along.
Pressure waves, compression waves, shock waves, expansion waves, sub-sonic waves, supersonic waves, Prandtl-Glauert singularity, fold catastrophe, cusp catastrophe, cusp bifurcations, fold bifurcation, pitchfork bifurcation, hysteresis loops, and more terms than you can imagine. I have finally arrived at the tipping point literally.

Don’t go there unless you really really want some brain candy. I have got to get this hand injury healed before I drive myself to the tipping point!

I wonder why Maldives ex-president Mohamed Nasheed’s supporters and international do not accept that Nasheed is mentally sick and he is the lier of the century. He should not be back in power. He could be the most currupted leader of the century too. He has robbed the assets of Maldives given to his supporters and has put the country in debt. International community should very carefully read the new constitution of Maldives. Nasheed’s cult do not understand the implications of their actions to the country. They are fighting back to come to the power to hide the illeagal actions. When Nasheed’s resignation was so sudden politians did not have time to remove or hide any evidence. Nasheed’s party, MDP members do not accept the constitution and laws they have endosed. Most of the MP’s supporting MDP is very currupt irresponsible people.